Plasmids were purified with the Endofree plasmid maxi kit (Sigma-Aldrich), injected in the lateral ventricle of E14.5 embryos in utero, and electroporated as previously described (Mire et al., 2012 (link)) using an electroporator (CUY21 Edit; Nepagene). Embryos were harvested in L15-glucose 48 h after electroporation. Brains were dissected and open or cut in the vibratome; the electroporated parts or the 100-µm sections were fixed in 10% ice-cold TCA for 20 min for pERM staining or in 4% PFA for 2 h for other stainings and processed for immunofluorescence as described previously (Deck et al., 2013 (link)).